1. Field of the Invention
The present invention relates to a technology for determining whether a target device such as an image forming apparatus is in a predictive failure state based on internal information of the target device.
2. Description of the Related Art
An image forming apparatus employing electrophotographic technology forms an electrostatic latent image induced by electrostatic charges on an image carrier such as photoconductive materials and attaches charged toner particles to the electrostatic latent image to form a visible image. The visible image formed of toner is finally transferred to a recording material such as paper and then is firmly established on the recording material by heat, pressure, solvent gas, and the like to become an output image. In such an image forming apparatus, the state of device associated with a series of imaging processes for forming an image changes gradually in accordance with the status of use. Therefore, to continue to provide a constant-quality image, it is necessary to regularly check out the state of various devices and unit in the image forming apparatus and perform parts replacement and supplement of consumables depending on the check result. This maintenance work is necessary in order to ensure smooth operation of the image forming apparatus.
A work for maintaining an image forming apparatus can be roughly classified into a regular maintenance that is performed regularly and an irregular maintenance that is performed irregularly when the image forming apparatus has failure or abnormality. The regular maintenance should be performed before the image forming apparatus does not reach an unavailable state. Therefore, parts replacement or the like is performed in a state where the spare available time of each part has a sufficient margin. As a result, the replaced part cannot be used for the spare available time. In this way, the number of parts replacements increases until the use of one image forming apparatus is finished. When the number of maintenances increases, a maintenance time increases. It leads to decrease productivity per one image forming apparatus.
In recent years, there has been proposed a system that monitors the state of an image forming apparatus, predicts whether the image forming apparatus is going to fail based on the change of state, and performs an irregular maintenance in accordance with the prediction result. A related technology has been disclosed in, for example, Japanese Patent Application Laid-open No. 2001-175328, Japanese Patent Application Laid-open No. 2007-328645, and Japanese Patent Application Laid-open No. H8-154161. In this way, by predicting the failure of the image forming apparatus and performing an irregular maintenance in place of a regular maintenance, various problems can be solved, such as the waste of spare available time or the degradation of productivity caused by the regular maintenance. Therefore, such a system has great social and economical values. Furthermore, this system has an advantage that an environmental impact can be largely reduced because an amount of use resource is largely reduced.
In general, the states of image forming apparatuses differ greatly depending on the status of use of each image forming apparatus, such as the type of output image, the number of outputs, an output-time interval, or a use environment. Therefore, to determine the state of each image forming apparatus with high precision, it is important that the state of each image forming apparatus should be grasped based on the internal information of each image forming apparatus. There is known a conventional method for determining whether an image forming apparatus is in a state (predictive failure state) indicative of a predictive failure based on the internal information of the image forming apparatus. However, in the conventional method, only two-valued information indicating whether a predictive failure is present or not can be obtained. In such two-valued information, there is a problem in that an appropriate maintenance service according to individual situations of each user cannot be provided because only the presence or absence of a predictive failure can be grasped.
For example, a user who wants to avoid the generation of down time as much as possible performs an early maintenance work in many cases even if the spare available time of part is wasted. On the other hand, a user who wants to use a part to the end of available time regardless of the generation of down time performs a maintenance work in many cases after preferably using the part for the available time even if the risk of down time is high. To provide an appropriate maintenance service according to individual situations for each user, it is important to grasp how much maintenance (emergency degree of maintenance) should be required at this time, in other words, what is a possibility (the size of failure risk) by which a failure occurs at this time. However, in the conventional method, the size of failure risk cannot be definitely grasped because two-valued information indicating whether a predictive failure is present or not is given. Therefore, in the conventional method, it was difficult to provide an appropriate maintenance service according to individual situations for each user.
Such a problem is not limited to an image forming apparatus and can occur in a device, an apparatus, and the like on which a maintenance work is performed.